Molten metal reactors may be used to treat a wide variety of waste materials including wastes which include halogenated hydrocarbons, biomedical waste, and radioactive wastes. Molten metal reactors utilize a bath of molten reactant metal which may include aluminum, magnesium, and/or lithium, for example, along with other metals. The atmosphere above the bath is preferably purged of oxygen. When waste material is placed in contact with the molten reactant metal, the metal reacts with the organic molecules in the waste material to strip halogen atoms and form metal salts. The reaction also liberates carbon along with other elements such as hydrogen and nitrogen. Carbon, hydrogen, nitrogen, and some metal salts may be removed from the molten metal reactor in a gaseous form. Metals which may be included in the waste material, or are liberated from the waste material, may alloy with the bath. Other reaction products or liberated materials collect at the surface or bottom of the bath and may be removed by suitable means.
Molten metal reactors require a heating arrangement to heat the reactant metal to a molten state and then maintain the reactant metal in a molten state at a desired temperature as waste material is added to the bath. U.S. Pat. No. 5,000,101 to Wagner shows a molten metal reactor having an induction heater for heating the reactant metal. U.S. Pat. No. 5,271,341 to Wagner discloses a two-chamber molten metal reactor having a hydrocarbon-fired heater in one of the chambers. This two-chamber arrangement allows the reactant metal to be heated with hydrocarbon-fired burners while maintaining a separate area in which reaction products may collect for removal.
Hydrocarbon-fired heaters are desirable for many molten metal reactor applications. However, other applications for molten metal reactors cannot accommodate heating using hydrocarbon-fired burners. For example, a molten metal reactor may be highly desirable for treating biomedical wastes and other wastes generated aboard a ship. However, a sufficient hydrocarbon supply may not be readily available aboard the ship to provide the required heating.
Induction heaters are well-suited for fixed plants which have access to a suitable electric power supply. However, the electromagnetic field produced by induction heaters has, prior to the present invention, limited the temperatures at which the molten metal reactor could be operated. This temperature limitation arose from the fact that portions of the electromagnetic field extended beyond the molten reactant metal and passed through the reactor vessel and related equipment. The electromagnetic field generated heat in these metallic structural elements as well as in the reactant metal. Therefore, structural elements associated with the molten metal reactor had to be comprised of metals which maintained strength at high temperatures. Operating temperatures still had to be kept low enough to maintain the structural integrity of structural elements associated with the molten metal reactor.
The temperature limitations associated with prior molten metal reactors also effectively limited the types of wastes which could be treated. For example, although wastes which included transuranic elements (all elements having an atomic number greater than uranium), could be treated in prior molten metal reactors, the treatment was slowed by the temperature of the molten metal bath. In prior art molten metal reactors, the molten metal temperature was insufficient to cause transuranic metals to go to a molten state. Thus, transuranic metals dissolved relatively slowly in prior art molten metal reactors, and the transuranic elements alloyed with the reactant metals only after this relatively slow dissolution process.